Deep in the recesses of the human heart, lurking guiltily beneath the threshold of consciousness, there may lie a depraved craving — for the forbidden taste of human flesh. The basis for this morbid accusation, made by a team of researchers in London, is a genetic signature, found almost worldwide, that points to a long history of cannibalism.

The signature is one that protects the bearer from infection by prions, proteins that can be transmitted in infected meat and attack the nerve cells of the brain. Prions can be acquired from eating infected animals, as in the case of the mad cow disease that in 1996 spread to people in England, but they spread even more easily through eating infected humans.
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The researchers then examined DNA from various ethnic groups around the world and found that all but one, the Japanese, carried the protective signature to some degree, and that the Japanese are protected by a different signature in the same gene.

Various genetic tests showed that the protective genes could not be there by chance, but were a result of natural selection. This implies that human populations in the past must have been exposed to some form of prion disease, the researchers say.